In recent years, those active in the tire industry have greatly increased their emphasis on the development of tires having both reduced rolling resistance and good wet traction properties. As is well known, that portion of the tire which exerts the greatest influence on rolling resistance and traction is the tread or tread rubber portion. Low rolling resistance is desirable from a fuel consumption standpoint while good wet traction is desirable from a performance standpoint. However, as a general rule, these properties have been found to conflict with each other. Thus, a reduction in rolling resistance generally leads to an almost directionally proportional reduction in wet traction while an increase in wet traction generally leads to an almost directionally proportional increase in rolling resistance.
The prior art has proposed a number of approaches to the solution of this problem. Such approaches have generally involved modifying the properties of the elastomer or elastomer composition utilized to form the tire tread in order to achieve the best possible balance between rolling resistance and traction. The approaches involving modification of the elastomer have generally been based on improving the interaction between the elastomer and the carbon black used in compounding the elastomer to prepare the tire tread composition. This had the effect of reducing the hysteresis of the tire tread composition which in turn results in low rolling resistance.
U.S. Pat. No. 3,135,716 to Uraneck et al teaches a process for making a terminally reactive polymer of conjugated diene monomers and, optionally, aryl substituted olefin monomers using an organo polylithium initiator. The terminal lithium atoms can be displaced by various compounds to form other terminally functionalized polymers.
U.S. Pat. No. 4,555,548 to Ueda et al discloses a polymer composition having benzophenone derivatives at the polymer terminals to improve rebound tread rubber compositions.
U.S. Pat. No. 4,616,069 to Watanabe et al teaches a process for making diene polymer rubber having alkali metal and/or alkaline earth metal terminals which can be reacted with aromatic or aliphatic amino organic compounds to produce a terminally functionalized polymer.
U.S. Pat. No. 4,015, 061 to Schulz et al discloses a N,N-bis(trialkylsilyl) amino-terminated polymer prepared by treating p-lithio-N,N-bis(trialkylsilyl) aryl amine with a diene monomer, which is converted to a mono- or di- primary aryl amine-ended diene polymer by direct acid hydrolysis.
Anionic Functional Initiators 1: 3-Dimethylaminopropyllithium as an Initiator for the Synthesis of Bi- and Difunctional Polybutadienes, M. J. Stewart, N. Shepherd, and D. M. Service, British Polymer Journal, Vol. 22, 319-325 (1990), discloses the use of 3-dimethylaminopropyllithium as an anionic initiator for the polymerization of butadiene.
Anionic Polymerization Initiated by Diethylamide in Organic Solvents. I. The Use of Lithium Diethylamide as a Polymerization Catalyst and the Effect of Solvent Type on the Polymerization of Isoprene and Styrene, A. C. Angood, S. A. Hurley, and P. J. T. Tait, Journal of Polymer Science: Polymer Chemistry Edition, Vol. 11, 2777-2791 (1973), discloses the use of lithium diethylamide as an initiator for the polymerization of isoprene.
"Anionic Polymerization", J. E. McGrath, Editor, American Chemical Society Symposium Series 166 (1981), discloses copolymerization of butadiene and styrene using various lithium-nitrogen-bonded initiators, such as lithium morpholinide, lithium dialkylamide, and lithium piperidinide.
A process for preparing a terminally functionalized polymer obtained by anionic polymerization of a diene monomer or mixture of a diene monomer and a vinyl aromatic hydrocarbon monomer is disclosed in U.S. Pat. No. 5,066,729 to Stayer, Jr. et al. The process comprises reacting the polymer with a compound having the formula: ##STR1## wherein R.sup.1 and R.sup.2 are selected from the group consisting of H, alkyl, cycloalkyl, aryl, dialkylaminoaryl, aralkyl, and aprotic O, N and S- containing alkyl, cycloalkyl, aryl, or aralkyl groups; wherein R.sup.3 is selected from the group consisting of alkyl, cycloalkyl, aryl, dialkylaminoaryl, aralkyl, and aprotic, O, N and S-containing alkyl, cycloalkyl, aryl and aralkyl groups; with the proviso that at least one of the R.sup.1, R.sup.2 and R.sup.3 groups must be a dialkylaminoaryl group and that not all of the R.sup.1, R.sup.2 and R.sup.3 groups can be aryl groups. The resultant terminally functionalized polymer has reduced hysteresis properties and may be utilized to prepare elastomer compositions and tire treads having reduced rolling resistance.
In U.S. Pat. No. 3,914,148 to Aboytes, a carbon black oxidized with a nitrogenous oxidizing acid is utilized in a conventional rubber formulation to provide better elastomer to metal bonding than similar compositions incorporating conventional channel blacks.
The use of nitric acid oxidized carbon black in a conventional rubber compound utilizing unmodified styrene-butadiene rubber to provide a rubber composition having a reduced modulus and an increased scorch time is taught by U.S. Pat. No. 4,075,140 to Hunt.